1. Field of the Invention
The present invention relates to an ink jet printer which hastens completion of the execution of a print job in the situation where a difference in ink temperature occurs depending on a position in a line type ink jet head and, further, in the case where the ink temperature of the ink jet head is out of an appropriate temperature range during execution of the print job.
2. Description of the Related Art
In general, the viscosity of ink that is used in an ink jet type printer is increased under a low temperature environment and is decreased under a high temperature environment. As a result, if the ink temperature is too high or too low, it becomes difficult for an ink jet head to discharge an appropriate amount of ink. Due to this, in the ink jet type printer, an appropriate temperature range when ink is used is determined so that an appropriate discharge operation can be performed.
Further, in the case where the overall width of a head is long and the head includes a plurality of head blocks, like a line type ink jet head, there is a problem that a difference in ink temperature occurs between the head blocks depending on the installation positions of the head blocks. That is, under a low temperature environment, since a head block that is installed near the center is surrounded by other head blocks, the ink temperature becomes relatively higher. By contrast, in a head block that is installed in an end portion, the amount of heat which is lost by the surroundings becomes larger, and thus the ink temperature becomes lowered. The tendency of the ink temperature of such an ink jet head appears noticeably under the low temperature environment.
In order to solve this problem, according to a technique described in JP-2004-322508A, the following control is performed so as to maintain a line type ink jet head that includes a plurality of head blocks at a predetermined temperature and to make the temperature of ink in all head blocks reach an appropriate temperature range.
That is, head blocks located near the end are assumed as one set, head blocks located in the center portion are assumed as one set, and temperature control using the same temperature sensing unit is performed with respect to the head blocks in the respective sets.